Jason came to me a few years ago looking for a way to track the popularity and correctness of comments on his site. I developed a solution that was great for him and his users and it has lasted over 3 years now without modification.
KLS LifeChange Ministries was looking for a better way to run their online training. I built a course and lesson builder that integrated with WordPress and WP eMember to allow the process of testing students to be completely editable and automated. It was a lesson both in the extensibility of WordPress and the expertise needed to build something that fit right in to the rest of the administrative interface.